Abstract

Around 1930 Ludwig Prandtl and his colleagues O. Tietjens and W. Müller published two films with visualizations of flows around surface piercing obstacles to illustrate the unsteady process of flow separation. These visualizations were achieved by recording the motion of fine particles sprinkled onto the water surface in water channels. The resulting images meet the relevant criteria of properly seeded recordings for particle image velocimetry (PIV). Processing these image sequences with modern PIV algorithms allows the visualization of flow quantities (e.g. vorticity) that were unavailable prior to the development of the PIV technique. The accompanying fluid dynamics video consists of selected original film sequences overlaid with visualizations obtained through PIV processing.